The Eye of Sauron

The Eye of Sauron, or Great Eye, was a symbol adopted by the Dark Lord in the late Second Age. It was said that few could endure its terrible gaze.

The Eye was used as a symbol on armor and banners of Mordor, representing Sauron's quasi-omniscience. It is unknown when the Eye of Sauron was formed.

At the apex of Barad-dûr, the Eye was a flaming, visible, though perhaps not tangible presence during the events of The Lord of the Rings, made clear when it appeared through a window when clouds parted in Mordor.